The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of persons skilled in the art.
Brassica seeds, including rapeseed, canola and mustard seeds, are a potential source of high quality protein suitable for human consumption. The defatted meals that can be obtained from these seeds contain about 40% w/w protein with a well-balanced amino acid composition, and have excellent functional properties. However, the use of Brassica seeds as a protein source is limited by the presence of certain undesirable toxic and anti-nutritional components, including glucosinolates, phytates, and phenolic compounds. The concentration of these undesirable components must be substantially reduced before these types of protein isolates are suitable for human consumption.
Glucosinolates are hydrolyzed in enzymatic reactions to form compounds that can interfere with thyroid function and cause liver and kidney damage at high concentrations. Phytates are strong chelating agents that bind to polyvalent metal ions in the body including iron, calcium and magnesium, rendering them unavailable for metabolism. Phenolic compounds impart an unpleasant bitter taste and a dark colour to the final protein products.
Phenolic compounds are particularly difficult to remove because some of the phenolics bind to the proteins in an aqueous media to form relatively large phenolic-protein complexes. Xu and Diosady (Food Res. Intl. 33:725 2000) characterized the canola protein-phenolic interactions in an aqueous media, using a series of chemical treatments followed by membrane separations. The results suggested that approximately 50% of the total extracted phenolic compounds formed complexes with canola proteins through ionic bonding (˜30%), hydrophobic interactions (<10%), hydrogen bonding (<10%), and covalent bonding (<10%). Although these figures may seem minor, if not removed, they could be concentrated to high phenolic compound levels in the protein isolates which represent only a small fraction of the meal mass.
In U.S. Pat. No. 4,889,921, Diosady et al. discloses a process for the production of protein isolates from rapeseed, including the steps of alkaline extraction and isoelectric precipitation to obtain a precipitate from which a first product stream of protein is recovered. The depleted solution from the precipitation stage is subjected to ultrafiltration followed by diafiltration and drying to obtain a second product stream of recovered protein. These two protein isolates were produced with a combined protein recovery of over 70% of the protein present in the seed. Both products were of high protein content (>90%), essentially free of glucosinolates (<2 mol/g), low in phytates (<1%), and had desirable functional properties for a variety of food applications. However, both of the protein isolates had an unpleasant bitter taste and a dark colour. These unacceptable organoleptic properties were attributable to the phenolic compounds that were left behind in the protein isolates.
In the U.S. Pat. No. 4,889,921 patent, membrane processes are used to concentrate and purify the protein isolates. These processes separate dissolved components on the basis of their molecular sizes. Specifically, the membranes reject and retain large molecules in the retentate, while allowing small molecules (impurities) to pass through into the permeate. These processes are effective at removing the glucosinolates and the phytates, as they are relatively small and pass through the pores of the membrane. However, the relatively large phenolic-protein complexes tend to be rejected by the membrane, and thus remain behind in the retentate along with the protein isolates. Further, the precipitate from the precipitation stage also includes phenolics and bound phenolics.
There still exists an ongoing need for a method for producing protein isolates derived from Brassica oil seeds that have low concentrations of glucosinolates, phytates and phenolic compounds.
Introduction
The following introduction is intended to introduce the reader to this specification but not to define any invention. One or more inventions may reside in a combination or sub-combination of the apparatus elements or process steps described below or in other parts of this document. The inventor does not waive or disclaim his rights to any invention or inventions disclosed in this specification merely by not describing such other invention or inventions in the claims.
The present invention provides a method for processing defatted oil seeds, comprising the steps of:                (a) solubilizing at least a portion of the protein contained in the oil seeds to produce suspended residual solids and a first solution comprising protein, phenolic-protein complexes, and free phenolic compounds;        (b) separating at least a portion of the free phenolic compounds from the first solution and recovering a free phenolic reduced solution; and        (c) treating the free phenolic reduced solution to precipitate at least a portion of the protein as a precipitated protein isolate and recovering a treated solution containing a soluble protein isolate.        
In one embodiment of the invention, the step of treating the free phenolic reduced solution to precipitate at least a portion of the protein comprises reducing the pH of the free phenolic reduced solution to form the precipitate.
In another embodiment of the invention, the step of separating at least a portion of the free phenolic compounds from the first solution comprises subjecting the first solution to membrane filtration to obtain the free phenolic reduced solution. Preferably, the membrane filtration comprises at least one of ultrafiltration, diafiltration and reverse osmosis.
In another embodiment of the invention, the method further comprises the step of treating at least a portion of the phenolic-protein complexes in the first solution in at least one point prior to step (b) to liberate at least some phenolic compounds from the phenolic-protein complexes.
In another embodiment of the invention, the step of treating the first solution comprises adding at least one salt to liberate at least a portion of the phenolic compounds from the phenolic-protein complexes.
In another embodiment of the invention the step of treating the first solution comprises the step of heating the first solution to liberate at least a portion of the phenolic compounds from the phenolic-protein complexes.
In one aspect of the invention, the temperature of the first solution is increased to between about 40° C. to about 75° C. In another aspect of the invention, the first solution is maintained at the increased temperature for a period of between about 10 to 180 minutes.
In another embodiment of the invention, the step of treating the first solution comprises adding at least one salt to liberate at least a portion of the phenolic compounds from the phenolic-protein complexes and the step of heating the first solution to liberate at least a portion of the phenolic compounds from the phenolic-protein complexes.
In another embodiment of the invention, the method further comprises the step of adding a surfactant to the first solution in at least one point prior to step (b) to liberate at least a portion of the phenolic compounds from the phenolic-protein complexes.
In another embodiment of the invention, the method further comprises the step of the adding a reducing agent to the first solution in at least one point prior to step (b) to inhibit the oxidation of at least a portion of the phenolic compounds.
In another embodiment of the invention, the method further comprises the steps of adding polyvinylpyrrolidone to the treated solution downstream of step (b) to adsorb at least a portion of the free phenolic compounds and removing the polyvinylpyrrolidone from the treated solution.
In another embodiment of the invention, the method further comprises the step of recovering at least a portion of the soluble protein isolate.
In another embodiment of the invention, the method further comprises the step of separating at least a portion of the suspended residual solids from the first solution prior to step (b), whereby a meal residue is obtained.
It will be appreciated that one or more of the above embodiments may be combined to obtain a method in accordance with the present invention.
The present invention also provides for a novel protein isolate comprising protein derived from mustard seeds. In one aspect of the invention, the mustard protein isolates may contain less than about 1% w/w phenolic compounds, preferably less than about 0.5% w/w phenolic compounds, more preferably less than about 0.2% w/w phenolic compounds, and most preferably less than about 0.02% w/w phenolic compounds.
In one aspect of the invention, the protein isolate is a precipitated protein isolate with protein in the range of between about 80% to about 110% w/w (N×6.25).
In another aspect of the invention, the protein isolate is a soluble protein isolate with protein in the range of between about 80% to about 110% w/w (N×6.25).
The present invention provides a protein isolate comprising protein derived from oil seeds when made by a method in accordance with the present invention comprising the steps of:                (a) solubilizing at least a portion of the protein contained in the oil seeds to produce suspended residual solids and a first solution comprising protein, phenolic-protein complexes, and free phenolic compounds;        (b) separating at least a portion of the free phenolic compounds from the first solution and recovering a free phenolic reduced solution; and        (c) treating the free phenolic reduced solution to precipitate at least a portion of the protein as a precipitated protein isolate and recovering a treated solution containing a soluble protein isolate.        
In one aspect of the invention, the oil seeds are Brassica seeds.
In another aspect of the invention, the oil seeds are chosen from one of canola seeds, rapeseeds or mustard seeds.
In another aspect of the invention, the oil seeds are mustard seeds.
In one aspect of the invention, the protein contains less than about 1% w/w phenolic compounds, preferably less than about 0.5% w/w phenolic compounds, more preferably less than about 0.2% w/w phenolic compounds, and most preferably less than about 0.02% w/w phenolic compounds.
The present invention provides a protein isolate comprising protein derived from oil seeds when made by a method in accordance with the present invention comprising the steps of:                (a) solubilizing at least a portion of the protein contained in the oil seeds to produce suspended residual solids and a first solution comprising protein, phenolic-protein complexes, and free phenolic compounds;        (b) treating at least a portion of the phenolic-protein complexes in the first solution to liberate at least some phenolic compounds from the phenolic-protein complexes;        (c) separating at least a portion of the free phenolic compounds from the first solution and recovering a free phenolic reduced solution; and        (d) treating the free phenolic reduced solution to precipitate at least a portion of the protein as a precipitated protein isolate and recovering a treated solution containing a soluble protein isolate.        
In one aspect of the invention, the oil seeds are Brassica seeds
In another aspect of the invention, the oil seeds are chosen from one of canola seeds, rapeseeds or mustard seeds.
In another aspect of the invention, the oil seeds are mustard seeds.
In one aspect of the invention, the protein contains less than about 1% w/w phenolic compounds, preferably less than about 0.5% w/w phenolic compounds, more preferably less than about 0.2% w/w phenolic compounds, and most preferably less than about 0.02% w/w phenolic compounds.
The present invention provides a protein isolate comprising protein derived from oil seeds when made by a method in accordance with the present invention comprising the steps of:                (a) solubilizing at least a portion of the protein contained in the oil seeds to produce suspended residual solids and a first solution comprising protein, phenolic-protein complexes, and free phenolic compounds;        (b) adding at least one salt to the first solution to liberate at least some phenolic compounds from the phenolic-protein complexes;        (c) separating at least a portion of the free phenolic compounds from the first solution and recovering a free phenolic reduced solution; and        (d) treating the free phenolic reduced solution to precipitate at least a portion of the protein as a precipitated protein isolate and recovering a treated solution containing a soluble protein isolate.        
In one aspect of the invention, the oil seeds are Brassica seeds.
In another aspect of the invention, the oil seeds are chosen from one of canola seeds, rapeseeds or mustard seeds.
In another aspect of the invention, the oil seeds are mustard seeds.
In one aspect of the invention, the protein contains less than about 1% w/w phenolic compounds, preferably less than about 0.5% w/w phenolic compounds, more preferably less than about 0.2% w/w phenolic compounds, and most preferably less than about 0.02% w/w phenolic compounds.
The present invention provides a protein isolate comprising protein derived from oil seeds when made by a method in accordance with the present invention comprising the steps of:                (a) solubilizing at least a portion of the protein contained in the oil seeds to produce suspended residual solids and a first solution comprising protein, phenolic-protein complexes, and free phenolic compounds;        (b) heating the first solution to liberate at least some phenolic compounds from the phenolic-protein complexes;        (c) separating at least a portion of the free phenolic compounds from the first solution and recovering a free phenolic reduced solution; and        (d) treating the free phenolic reduced solution to precipitate at least a portion of the protein as a precipitated protein isolate and recovering a treated solution containing a soluble protein isolate.        
In one aspect of the invention, the oil seeds are Brassica seeds.
In another aspect of the invention, the oil seeds are chosen from one of canola seeds, rapeseeds or mustard seeds.
In another aspect of the invention, the oil seeds are mustard seeds.
In one aspect of the invention, the protein contains less than about 1% w/w phenolic compounds, preferably less than about 0.5% w/w phenolic compounds, more preferably less than about 0.2% w/w phenolic compounds, and most preferably less than about 0.02% w/w phenolic compounds.
The present invention also provides for a food product suitable for human consumption, comprising a protein derived from mustard seeds. In one aspect of the invention, the protein contains less than about 1% w/w phenolic compounds, preferably less than about 0.5% w/w phenolic compounds, more preferably less than about 0.2% w/w phenolic compounds, even more preferably less than about 0.1% w/w phenolic compounds, and most preferably less than about 0.02% w/w phenolic compounds.
In one embodiment of the present invention, the food product is a processed meat product.
In another embodiment of the present invention, the food product is a vegetarian meat substitute.
In another embodiment of the present invention, the food product is a bakery product.
In another embodiment of the present invention, the food product is a nutritional supplement.
In another embodiment of the present invention, the food product is an infant formulation.
In another embodiment of the present invention, the food product is a bar.
In another embodiment of the present invention, the food product is a drink.
The present invention also provides for a food product suitable for human consumption, comprising a carbonated drink comprising a soluble protein isolate derived from oil seeds.
In one aspect of the invention, the oil seeds are preferably Brassica oil seeds, more preferably oil seeds chosen from one of canola seeds, rapeseeds, or mustard seeds, and most preferably mustard seeds.
In another aspect of the invention, the soluble protein isolate contain less than about 1% w/w phenolic compounds, preferably less than about 0.5% w/w phenolic compounds, more preferably less than about 0.2% w/w phenolic compounds, and most preferably less than about 0.02% w/w phenolic compounds.